log日志是这样的

02-01 19:01:54.192    4753-4753/com.example.administrator.guessmusic E/MediaPlayer-JNI﹕ QCMediaPlayer mediaplayer NOT present

02-01 19:01:54.192    4753-4753/com.example.administrator.guessmusic W/System.err﹕ java.io.FileNotFoundException: coin.mp3

02-01 19:01:54.192    4753-4753/com.example.administrator.guessmusic W/System.err﹕ at android.content.res.AssetManager.openAssetFd(Native Method)

02-01 19:01:54.192    4753-4753/com.example.administrator.guessmusic W/System.err﹕ at android.content.res.AssetManager.openFd(AssetManager.java:339)

02-01 19:01:54.192    4753-4753/com.example.administrator.guessmusic W/System.err﹕ at com.example.administrator.guessmusic.MyPlayer.playSong(MyPlayer.java:37)

37行附近的代码是这样

try{

 AssetFileDescriptor fileDescriptor = assetManager.openFd(fileName);/* 有什么问题 */       mMusicMediaPlayer.setDataSource(fileDescriptor.getFileDescriptor(),fileDescriptor.getStart  Offset(),fileDescriptor.getLength());

 mMusicMediaPlayer.prepare();

 }catch (IOException e){

 e.printStackTrace();

 }